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best estimates of things like the hubble parameter, dark energy density, baryon matter density, dark matter, and so on


new WMAP data might be coming out this month that could cause some of these numbers to be revised, but this is a clear concise summary of the current estimates with some intersecting bubble diagrams that communicate some of how they are arrived at

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we have been using Ned Wright's cosmology calculator here at SFN for over two years now.

it was one of the first things I posted about at beginning of this thread.


here is a writeup about the calculator


A Cosmology Calculator for the World Wide Web

Edward L. Wright (UCLA)

8 pages with 1 included figure. Cosmology calculator available at this http URL, light travel time converter at this http URL and the advanced cosmology calculator at this http URL


"A cosmology calculator that computes times and distances as a function of redshift for user-defined cosmological parameters is available on the World Wide Web. This note gives the formulae used by the cosmology calculator and discusses some of its implementation. A version of the calculator that allows one to specify the equation of state parameter w and w' and neutrino masses, and a version for converting the light travel times usually given in the popular press into redshifts are also available."

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It may interest some of you :


On Sunday, Nov. 19th, Earth will pass through a stream of debris from comet 55P/Tempel-Tuttle. The result: a shower of Leonid meteors.


"We expect an outburst of more than 100 Leonids per hour," says Bill Cooke, the head of NASA's Meteoroid Environment Office in Huntsville, AL.


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Updating some basic cosmology links:

Ned Wright's cosmology tutorial



Ned Wright's cosmology FAQ



Ned Wright's most basic cosmology calculator


(he has links to some more advanced or specialized calculators)


Morgan's calculator



Murphy's coordinate conversion tool



Lineweaver and Davis' Scientific American article Misconceptions about the big bang March 2005.





Here are the links to the same article at the SciAm website. But these links have been going dead or else the GRAPHICS that you used to get have been disappearing. So these SciAm links may not be as good as the Princeton one




The Lineweaver Davis article had some very useful SIDEBARS giving pictorial diagrams with a question together with right and wrong answers explained. For easier access, here are links to individual sidebars.



What kind of explosion was the big bang?



Can galaxies recede faster than light?



Can we see galaxies receding faster than light?



Why is there a cosmic redshift?



How large is the observable universe?



Do objects inside the universe expand, too?

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Some recent cosmology data and estimates:

Komatsu et al (WMAP 5th year data, cosmology implications)



They publish a lowerbound estimate for the radius of curvature of the universe--95 percent confidence level.

See Figure 2 on page 4 and convert the units to lightyears

( 23 *(1/0.72)*3.26 billion lightyears = 104 billion lightyears )

A 'best fit' estimate derived from Ned Wright's January paper was 130 billion lightyears, not far from their lower bound.


So space might have infinite volume but it also might very well have finite. And if it has finite volume then they are telling us the length of the longest possible straight line is AT LEAST 2 pi times 104 billion lightyears-----in other words about 650 billion LY.


That's the idea of giving a lower bound. The circumference has to be at least 650 billion LY. It could be more, and it could be infinite, but with 95% confidence it cannot be less. If you could travel at a billion times c, then you could start out from earth and travel in the straightest possible line for at least 650 years before getting back to square one.

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What a great list of resources.


I have been putting together a list of books, magazines, and news sources for people interested in astronomy and other fields in science and technology. The site is Explore-Science.net.


Great Astronomy Books is a growing list of the best reads in astronomy.


The Astronomy Magazines page presents the top picks for astronomy articles.


Finally, the Astronomy News section gathers the best sources on the web for astronomy discoveries and research.

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Now since the Sun is very active and Space Weather is a hot topic. You may find this book interesting..comes with online multimedia material.






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some might find this interesting or useful,




" If you're running on Chrome browser, check out Google's latest Experiment project - it visualizes the precise location of at least 100,000 stars in our Milky Way galaxy, using various imagery and data pulled from NASA and the European Space Agency (ESA). For your frame of reference, there are approximately 200 to 400 billion stars in the Milky Way galaxy. "




zoom in all the way to see the sun,zoom all the way out to see the galaxy.

or everything in between.

you can grab this with your mouse and move any axis's plane.

take the tour that's provided.

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